[linux-dvb] Preliminary support of Hauppauge Nova-T 500Dual(take2)

hermann pitton hermann-pitton at arcor.de
Wed Sep 20 03:13:53 CEST 2006


Am Dienstag, den 19.09.2006, 20:31 -0400 schrieb Steven Toth:
> hermann pitton wrote:
> > Hi,
> >
> > Am Dienstag, den 19.09.2006, 16:51 -0400 schrieb Steven Toth:
> >   
> >>>> In the windows driver we leave the LNA off at all times, but have a registry
> >>>> override to allow users to enable it. It's a single LNA for both tuners -
> >>>> hence, it has its problems.
> >>>>
> >>>> Switching the LNA dynamically in a TV app isn't something the API allows. How
> >>>> about a module load param?
> >>>>     
> >>>>         
> >>> As updating an LNA (or something else) is very board specific, I put 
> >>> callback "update_lna" in dib3000mc_config. I will call this after starting 
> >>> the AGCs to see if the LNA has to be turned on or not (taking the agc 
> >>> response into account). For that I would like to know, what is the gain of 
> >>> the LNA when turned on? (So that I can adjust the thresholds when to turn 
> >>> on or off). Maybe we need to make an average of both channels, not that we 
> >>> kill one channel by only taking the other one into account. 
> >>>
> >>> Or is a module_parameter enough? (I don't like this, because the majority 
> >>> of users does not even now what is a module, which is good).
> >>>   
> >>>       
> >> Image a user that lives somewhere between two broadcast towers. They 
> >> receive some muxes at fairly weak levels and some very strong 
> >> (environment depending). We never found a good automatic solution to 
> >> deal with that within the (windows) driver.
> >>
> >> If the driver can be made to work reliably for all users in Linux under 
> >> all circumstances then that's ideal. :)
> >>
> >> Otherwise, the user may need some way to dictate LNA behavior.
> >>     
> >
> > looks like it is all because we are poor hackers ;)
> >
> >   
> 
> On the contrary.
> 
> > With reliable data sheets signal strength and/or ber rates should
> > indicate when to switch.
> >
> >   
> 
> Last I looked Dibcom and Microtune hadn't released public datasheets for 
> their parts.
> 
> If tuner 1 is active on a strong mux, enabling a single LNA for tuner 2 
> (so a weak signal can be selected) may end up adding 10db to tuner 1 
> leading to problems.
> 
> I'm simply saying be careful with implementing policy for a single LNA 
> that effects multiple tuners, especially if the user has no choice about 
> how the LNA is controlled.

OK, this is again a special case to be more competitive, like removing
the firmware eeprom on the current asus p7131 dual.

> > Looks similar like the situation on analog radio. Guess _nobody_ knows
> > how to read auxiliary bits and recently a little more for all tuners
> > around to get at least stereo/signal strength ...
> >
> >   
> A lot of datasheets are available for tuners. I don't know why this 
> would be a problem if someone decided to implement it.

No, that is not true without NDAs recently and was the same for people
working on it previously. Example is radio on tda8275ac1 and saa7131e.

Cheers,
Hermann





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